The Tosafot, Tosafos or Tosfot are medieval commentaries on the Talmud. They take the form of critical and explanatory glosses, printed, in almost all Talmud editions, on the outer margin and opposite Rashi's notes.
The first page of the Vilna Edition Shas of the Babylonian Talmud, tractate Berakhot, folio 2a. The main text in the middle is the text of the Talmud itself. To the right, on the inner margin of the page, is Rashi's commentary; to the left, on the outer margin, the Tosafot
The Talmud is the central text of Rabbinic Judaism and the primary source of Jewish religious law (halakha) and Jewish theology. Until the advent of modernity, in nearly all Jewish communities, the Talmud was the centerpiece of Jewish cultural life and was foundational to "all Jewish thought and aspirations", serving also as "the guide for the daily life" of Jews.
An early printing of the Talmud (Ta'anit 9b); with commentary by Rashi
A page of a medieval Jerusalem Talmud manuscript, from the Cairo Geniza
A full set of the Babylonian Talmud
Koren Talmud Bavli